It took me a few months of preparation using the book I mentioned in your other thread to get a good enough grip on it to feel that I could tackle the exam. This is going to vary based on how much time you can dedicate to preparation for the test - I was preparing for mine around a few other things, including work. (On the other hand, I did fairly well on it using that method, so...)

Theodore Jonathan Casser
SCJP/SCSNI/SCBCD/SCWCD/SCDJWS/SCMAD/SCEA/MCTS/MCPD... and so many more letters than you can shake a stick at!